A bone density test is very similar to an X-ray where the person undergoing the test lies on a padded platform, and a mechanical arm moves over them, according to Mayo Clinic. The test takes from 10 to 30 minutes, and radiation output is lower than a chest X-ray.
In most cases, a bone density test is done on bones that are likely to break due to osteoporosis, such as the bones in the lower spine, the neck of the femur and the bones of the forearm, claims Mayo Clinic. Though most tests are done in a hospital, small, portable peripheral machines may be available at pharmacies for those interested in bone density. These tests are often less expensive than tests done in a hospital.
It is important for individuals to understand that bone density may vary from one part of the body to another, explains Mayo Clinic. A reading done on the ankle, for instance, is not a good indicator of the bone density of the forearm. Since this is the case, a doctor may suggest that patients who receive a positive result for osteoporosis on a peripheral machine go for a bone density scan at the hospital. The hospital scan looks at areas, such as the hip, and can confirm an osteoporosis diagnosis.